Internet Engineering Task Force (IETF) K. Zeilenga
Request for Comments: 6171 Isode Limited
Category: Standards Track March 2011
ISSN: 2070-1721
The Lightweight Directory Access Protocol (LDAP) Don't Use Copy Control
Abstract
This document defines the Lightweight Directory Access Protocol
(LDAP) Don't Use Copy control extension, which allows a client to
specify that copied information should not be used in providing
service. This control is based upon the X.511 dontUseCopy service
control option.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6171.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Zeilenga Standards Track [Page 1]
RFC 6171 LDAP Don't Use Copy Control March 2011
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
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material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
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outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
1. Background and Intended Usage
This document defines the Lightweight Directory Access Protocol
(LDAP) [RFC4510] Don't Use Copy control extension. The control may
be attached to request messages to indicate that copied (replicated
or cached) information [X.500] is not be used in providing service.
This control is based upon the X.511 [X.511] dontUseCopy service
control option.
The Don't Use Copy control is intended to be used where the client
requires the service be provided using original (master) information
[X.500]. In absence of this control, the server is free to make use
of copied (i.e., non-authoritative) information in providing the
requested service.
For instance, a client might desire to have an authoritative answer
to a question of whether or not a particular user is a member of a
group. To ask this question of a server, the client might issue a
compare request [RFC4511], with the Don't Use Copy control, where the
entry parameter is the Distinguished Name (DN) of the group, the
ava.attributeDesc is 'member', and the ava.assertionValue is the DN
of the user in question. If the server has access to the original
(master) information directly or through chaining, it performs the
operation against the original (master) information and returns
compareTrue or compareFalse (or an error). If the server does not
have access to the original information, the server is obligated to
either return a referral or an error.
It is not intended that this control be used generally (e.g., for all
LDAP interrogation operations) but only as required to ensure proper
directory application behavior. In general, directory applications
ought to designed to use copied information well.
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RFC 6171 LDAP Don't Use Copy Control March 2011
2. Terminology
DSA stands for Directory System Agent (or server).
DSE stands for DSA-Specific Entry.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
3. The Don't Use Copy Control
The Don't Use Copy control is an LDAP Control [RFC4511] whose
controlType is 1.3.6.1.1.22 and controlValue is absent. The
criticality MUST be TRUE. There is no corresponding response
control.
The control is appropriate for LDAP interrogation operations,
including Compare and Search operations [RFC4511]. It is
inappropriate for all other operations, including Abandon, Bind,
Delete, Modify, ModifyDN, StartTLS, and Unbind operations [RFC4511].
When the control is attached to an LDAP request, the requested
operation MUST NOT be performed on copied information. That is, the
requested operation MUST be performed on original information.
If original (master) information for the target or base object of the
operation is not available (either locally or through chaining), the
server MUST either return a referral directing the client to a server
believed to be better able to service the request or return an
appropriate result code (e.g., unwillingToPerform).
It is noted that a referral, if returned, is not necessarily to the
server holding the original (master) information. It is also noted
that an authoritative answer to the question might not be available
to the client for any number of reasons.
Where the client chases a referral to a server (as referenced by an
LDAP URL) in the server response in order to obtain an authoritative
response, the client MUST provide the dontUseCopy control with the
interrogation request it makes to the referred to server. While LDAP
allows return of other kinds of URIs, the syntax and semantics of
other kinds of URIs are left to future specifications. The
particulars of how to act upon other kinds of URIs are also left to
future specifications.
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RFC 6171 LDAP Don't Use Copy Control March 2011
Servers implementing this technical specification SHOULD publish the
object identifier 1.3.6.1.1.22 as a value of the 'supportedControl'
attribute [RFC4512] in their root DSE. A server MAY choose to
advertise this extension only when the client is authorized to use
it.
4. Security Considerations
This control is intended to be provided where providing service using
copied information might lead to unexpected application behavior.
Use of the Don't Use Copy control may permit an attacker to perform
or amplify a denial-of-service attack by causing additional server
resources to be employed, such as when the server chooses to chain
the request instead of returning a referral. Servers capable of such
chaining can mitigate this threat by limiting chaining to a
particular group of authenticated entities.
LDAP is frequently used for storage and distribution of security-
sensitive information, including access control and security policy
information. Failure to use the Don't Use Copy control may thus
permit an attacker to gain unauthorized access by allowing reliance
on stale data.
5. IANA Considerations
5.1. Object Identifier
IANA has assigned an LDAP Object Identifier [RFC4520] to identify the
LDAP Don't Use Copy Control defined in this document.
Subject: Request for LDAP Object Identifier Registration
Person & email address to contact for further information:
Kurt Zeilenga <Kurt.Zeilenga@Isode.COM>
Specification: RFC 6171
Author/Change Controller: IESG
Comments:
Identifies the LDAP Don't Use Copy Control
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RFC 6171 LDAP Don't Use Copy Control March 2011
5.2. LDAP Protocol Mechanism
IANA has registered this protocol mechanism [RFC4520] as follows.
Subject: Request for LDAP Protocol Mechanism Registration
Object Identifier: 1.3.6.1.1.22
Description: Don't Use Copy Control
Person & email address to contact for further information:
Kurt Zeilenga <Kurt.Zeilenga@Isode.COM>
Usage: Control
Specification: RFC 6171
Author/Change Controller: IESG
Comments: none
6. Acknowledgements
The author thanks Ben Campbell, Phillip Hallam-Baker, and Ted Hardie
for providing review and specific suggestions.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4510] Zeilenga, K., Ed., "Lightweight Directory Access Protocol
(LDAP): Technical Specification Road Map", RFC 4510, June
2006.
[RFC4511] Sermersheim, J., Ed., "Lightweight Directory Access
Protocol (LDAP): The Protocol", RFC 4511, June 2006.
[RFC4512] Zeilenga, K., Ed., "Lightweight Directory Access Protocol
(LDAP): Directory Information Models", RFC 4512, June
2006.
7.2. Informative References
[X.500] International Telecommunication Union - Telecommunication
Standardization Sector, "The Directory -- Overview of
concepts, models and services," X.500(1993) (also ISO/IEC
9594-1:1994).
[X.511] International Telecommunication Union - Telecommunication
Standardization Sector, "The Directory: Abstract Service
Definition", X.511(1993) (also ISO/IEC 9594-3:1993).
Zeilenga Standards Track [Page 5]
RFC 6171 LDAP Don't Use Copy Control March 2011
[RFC4520] Zeilenga, K., "Internet Assigned Numbers Authority (IANA)
Considerations for the Lightweight Directory Access
Protocol (LDAP)", BCP 64, RFC 4520, June 2006.
Author's Address
Kurt D. Zeilenga
Isode Limited
EMail: Kurt.Zeilenga@Isode.COM
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